Human lie detector’s not admissible, still, a strong circuit trend. This is consistent with military appellate case law.
With expert testimony admitted on a wide range of issues under FRE 702, what limits are there to expert testimony on the credibility of the defendant? As noted by the Tenth Circuit, a consensus in disallowing this expert testimony has emerged among the circuits; plain error resulted from the admission of this expert testimony requiring reversal of the conviction, inUnited States v. Hill, _ F.3d _ (10th Cir. April 28, 2014) (No. 12-5154)
One area of expertise may involve determining whether a witness is credible. Certain specialized training and techniques have been developed to gauge the credibility of a witness during an interview. While this expertise may be useful and employed during an interview, it is generally inadmissible at trial under FRE 702. The Tenth Circuit reviewed and reinforced its exclusion of such expert testimony, finding such exclusion the practice of other circuits as well. While there was no objection lodged at trial to the expert testimony, the circuit found the admission of this expert testimony constituted plain error.